Gallic Wars (De Bello Gallico), sometimes The Conquest of Gaul, is an account written by Julius Caesar about his nine years of war in Gaul. In it Caesar vividly describes the battles and intrigues that took place in the nine years he spent slaughtering tribal armies that opposed Roman domination. The "Gaul" that Caesar refers to is sometimes all of Gaul except for the Provincia Narbonensis (modern day Provence), encompassing all of modern France, Belgium and some of Switzerland. In other occasions he refers only to that territory inhabited by the Celts (that Romans called Gauls), from the Channel to Lugdunum (Lyon).

The first book describes Gaul and the campaign against the Helvetii, a tribe living just outside Provence in Switzerland, who decided to migrate to the lowland regions of France to the west due to population pressures. This would require moving through either Provence, or areas held by various tribes allied to Rome. When Caesar made it clear he would not allow this, an alliance of various tribes formed to fight him. This drew the Romans out of Provence. Later books are about the campaigns against Veneti, Aquitani, Germans and Bretons; Caesar's invasions of Britain; the insurrection of Gaul (VII, 4) and the defeat of Vercingetorix at Alesia (VII, 89).

Campaigns typically started in late summer with the provisioning of grain and construction of fortresses, ending late in the year when Caesar returned to Italy for the winter. He campaigned with a number of legions in his army, sometimes as many as eight. He faced a variety of tribal armies, often hasty alliances of them, some numbering – at least in claim – over 100,000 strong. Many of the campaigns end with the Roman cavalry running down thousands of fleeing tribesmen, often their women and children as well. In one instance he defeated a tribe and immediately sold all 53,000 survivors into slavery.

After the second year of campaigning many of the hostile tribes had been decimated and much of Gaul was under Roman control to some degree. By this point any threat to the province, or to Rome itself, was dubious at best. It has been noted that the book could also serve in Caesar's intentions as an answer to his political opponents, who questioned the real need of this costly war, one of the most expensive in their history. Many of the reasons provided clearly stretch the credibility of its readers. For instance, his reasons for invading Britain came down to noting that while fighting in north-west Gaul, local armies were often supported by mercenaries from Britain.

It is often lauded for its polished, clear Latin. This book has traditionally been the first authentic text assigned to students of Latin, as Xenophon's Anabasis was for students of Greek. It is therefore not always remembered with affection. On the other hand, a literary classic in an ancient language that can be read by high-school students is a rare thing. On re-reading it in later life, many people can perceive the clarity of syntax and beauty of style of which an early Latin teacher tried to convince them. The style is indeed simple and elegant, essential and not rhetorical, dry as a chronicle, yet rich of details.

Also, the books are valuable for the many geographical and historical facts (Gallia est omnis divisa in partes tres...) that can be retrieved from this book, which was also one of the earliest to be written in third person. Notable chapters regard Gauls' costumes (VI, 13), their religion (VI, 17), a comparison between Gauls and Germans (VI, 24) and other curious notes like the little interest Germans had for agriculture (VI, 22).